Transportation systems of this general type are known, for example, from U.S. Pat. Nos. 3,340,821, 3,502,038 and 3,636,883. Such a system, as described in these earlier patents, may comprise one or more transporters in the form of self-propelled carriages riding on an endless track past the several receiving stations. The carriages may be provided with destination-indicating code markings for the selective closure of circuits, e.g. with the aid of magnetic switches, which control the shunting of an oncoming carriage onto a siding at the desired receiving station.
Such an internal transportation system is useful in many enterprises in which stacks of paper or other relatively bulky articles are to be sent from one station to another. For simpler articles such as individual sheets or plates, or for sensitive goods which must not be bunched or stacked, the use of an entire carriage destined for a single receiving station is cumbersome and uneconomical. In a printing plant of a major newspaper, for example, forms prepared in the composing room must be quickly delivered to respective offset machines at a number of printing stations, these forms requiring careful handling during transportation.